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Optimized network re-entry in a wireless communications network

Optimized network re-entry in a wireless communications network description/claims

The present application claims priority from a provisional application Ser. No. 60/895,228, entitled “OPTIMIZED NETWORK RE-ENTRY IN A WIRELESS COMMUNICATIONS NETWORK,” filed Mar. 16, 2007, which is commonly owned and incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates generally to communication systems and, more particularly, to supporting network re-entry from idle mode and handover in communication networks.

2. Background of the Invention

Idle mode allows a mobile station to become periodically available for downlink broadcast traffic messaging without registering at any specific base station. Indeed, the mobile station can remain in idle mode while it traverses a large geographic area populated by multiple base stations. Idle mode restricts mobile station activity to scanning at specific intervals and relieves requirements for the mobile station to perform handovers and other air interface tasks, thereby conserving mobile station power and other operational resources. Idle mode also benefits the network by providing a simple and timely method for alerting the mobile station to pending downlink traffic directed toward the mobile station, and by eliminating air interface and network handover traffic for inactive mobile stations.

When a mobile station initiates network re-entry from idle mode or idle mode exit at a new target base station which has no previous context for the mobile station, a number of sequential request messages, followed by a number of sequential response messages, are required to complete the re-entry. For example, in an IEEE 802.16e based system (e.g. WiMAX), the mobile station may send a first message, such as a range request (RNG-REQ) message, to a base station controlled by a target access service network (ASN) in order to initiate idle mode exit. Before the target ASN can respond to the first message, however, it must send a second mobile station state change request, along with a paging controller update, to an anchor paging controller/location register (PC/LR) function that is associated with the mobile station. Before the anchor PC/LR can respond to the state change request, it then must send a third message in the form of a context request to an anchor authenticator function that is associated with the mobile station in order to retrieve authenticator context associated with the mobile station.

After the PC/LR receives a response to the context request, it then can generate its own response to the state change request, which may include the authenticator context that authenticates the mobile station and an identifier for an anchor date path function. Once the mobile station is authenticated, the target ASN may then send a message to the anchor date path function associated with a foreign agent for the mobile station. This message can request that a data path bearer connection be established between the foreign agent and the base station controlled by the target ASN.

In some circumstances, for instance when network resources are heavily loaded, such serial communication exchanges can take significant periods of time to complete, resulting in an unacceptable user experience. Moreover, the length of time required for the mobile station to complete idle mode exit diminishes the energy saving benefits of the idle mode feature. In consequence, the idle mode feature is less likely to be used, which can lead to increased traffic in a communications network.

Mobile stations also may handover from one base station to another. When handover is desired, the mobile station can relay its intent to perform a handover by notifying its current serving ASN. The serving ASN, in turn, can notify the target base station(s), or target ASN(s) that control the potential target base stations, to which the mobile station may attempt to handover. The target base stations then may allow non-contention-based initial ranging opportunities and dedicated bandwidth allocations for the mobile station to support handover ranging.

For various reasons (e.g. rapidly changing air interface conditions, a mobile station entering an elevator or tunnel, poorly engineered networks, etc.) a target base station may not receive prior notification of an impending handover of a mobile station from the mobile station's current serving ASN. When such a handover occurs, it is treated as an unsolicited handover. When the target base station is controlled by an ASN that is different than the mobile station's current ASN, the unsolicited handover is known as an unsolicited inter-ASN handover.

The mobile station may initiate an unsolicited handover by anonymously sending a RNG-REQ message to a target base station in order to initiate handover ranging using a CDMA ranging code. When the mobile station ranges in this manner, it may not receive enough bandwidth from the target base station to complete handover ranging in a timely manner, if at all. Moreover, in order to complete the handover, the target ASN must receive identifiers for the anchor data path function ASN and anchor authenticator ASN, and latest media access control (MAC) context associated with the mobile station. However, since the target ASN has no context for the mobile station, before the target ASN can know from which anchor authenticator ASN it can retrieve authenticator context for the mobile station and with which anchor data path ASN it must initiate data path registration, the target ASN must first request context for the mobile station from the prior serving base station/ASN that was previously associated with the mobile station. Thus, a long series of messages must be communicated among network resources before an unsolicited handover can be completed, thereby resulting in greater latency delays in comparison to a controlled handover in which the serving base station/ASN is notified of the impending handover by the mobile station and is able to notify the target base station(s)/ASN(s) of a potential impending handover. These latency delays can be compounded by signaling delays in the network, and in some circumstances can take several seconds to complete, thereby resulting in poor handover performance and, in some cases, failure of real-time applications supported by the mobile station prior to the handover.

The present invention relates to a method for supporting entry of a remote unit onto an access service network (ASN). The entry can be, for example, re-entry from idle mode or a handover from another base station. The method can include receiving a message from the remote unit that includes an authenticator identifier, and requesting contextual information associated with the remote unit from an authenticator function corresponding to the authenticator identifier.

In another arrangement, the method can include receiving a message from the remote unit that includes a data path identifier and requesting establishment of a bearer path connection for the remote unit from a foreign agent corresponding to the data path identifier.

The present invention also relates to a method for supporting entry of a remote unit onto an ASN. The method can include, from the remote unit, sending a request to establish network presence at the ASN. The request can include an authenticator identifier. The method also can include, at the remote unit, receiving a response to the request from the ASN.

In another arrangement, the method can include, from the remote unit, sending a request to establish network presence at an ASN. The request can include a data path identifier. The method also can include, at the remote unit, receiving a response to the request from the ASN.

• Provisional Patent
• Utility Patent

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